1. Field of the Invention
The present invention generally relates to a reflective-type liquid crystal display and a method for manufacturing the same and, more particularly, to a system integrated reflective-type liquid crystal display (SIRLCD) and a method for manufacturing such a SIRLCD, in which a conductive plug is disposed on each of a plurality of pre-determined positions on a substrate so as to form an interface module for connecting an optical module by using well-developed LCD manufacturing processing and a control module by using well-developed semiconductor manufacturing processing, independently, thereby improving the product yield and reducing the fabrication cost.
2. Description of the Prior Art
Recently, with the high development in opto-electronics and semiconductor manufacturing processing, people have increasing needs for high-resolution displays such as LCD""s. Therefore, the industry has developed a liquid crystal on silicon (LCOS) display with high resolution by combining a liquid crystal optical module for display and a semiconductor integrated circuit (IC) for control.
In FIG. 1, a cross-sectional representation of a conventional LCOS display or a SIRLCD is shown. A starting semiconductor structure has an upper layer of silicon (Si) and is understood to possibly include a semiconductor substrate 10, active devices such as metal-oxide-semiconductor (MOS) transistors and passive devices such as capacitors. One of the MOS transistors includes a drain 18, a source 20 and a gate electrode 16 formed on a gate oxide 14. The MOS transistor is isolated from adjacent semiconductor devices by isolating regions 13. Moreover, one of the capacitors with a bottom electrode 22 is formed on the isolating region 13. A dielectric layer 19 is formed on the bottom electrode 22, and then a top electrode 17 is further formed on the bottom electrode 22. A first insulating layer 21 is formed of silicon dioxide covering the transistor and the capacitor on the substrate 10 so as to protect and isolate the electronic devices.
After the formation of the first insulating layer 21, openings are formed by etching the insulating layer at the positions of the drain 18, the source 20 and the top electrode 17 so as to form contacts 45, 55 and 25 connected to the drain 18, the source 20 and the top electrode 17, respectively, by filling the opening with conductive materials such as titanium, titanium nitride, tungsten and aluminum. Conductive wires 63 and 64 are formed of metal deposited and patterned on the first insulating layer 21. The conductive wire 64 is connected to the drain 18 through the contact 45, while the conductive wire 63 is connected to the source 20 and the top electrode 17 through the contact 55 and 25, respectively.
A second insulating layer 23 is formed covering the conductive wires 63 and 64 on the first insulating layer 21. A light-shielding layer 77 is formed on the second insulating layer 23 comprised of metal materials such as titanium, titanium nitride and tungsten, thereby shielding or absorbing the diffracted light and preventing the diffracted light from affecting or interfering the MOS transistors and capacitors because of the photoelectric effect. After the surface of the light-shielding layer 77 is covered by a third insulating layer 71 formed of silicon dioxide, pixel electrodes 79 are disposed on corresponding pre-determined positions on the surface of the third insulating layer 71. One of the pixel electrodes 79 is electrically connected to the corresponding conductive wire 63 through the via 35.
A protective layer 36 is formed on the pixel electrodes 79 not only to protect the pixel electrodes 79 but also to enhance light reflection. A liquid crystal module is disposed on the protective layer 36 to comprise at least one liquid crystal layer 30 sandwiched between alignment films 33 and 37. A transparent electrode 38 is provided on the alignment film 37, on which a transparent substrate 40 is formed so as to protect the liquid crystal module.
However, in the aforementioned LCOS display, if only a protective layer 36 is disposed on the pixel electrodes 79, it is very likely that a notch may be formed between the pixel electrodes 79. In addition, the alignment film 33 on the protective layer 36 may also affect the alignment of liquid crystal molecules because the alignment film 33 is not sufficiently flat. Those who are skilled in the art manage to fill the gap with filler made of dielectric materials 73 between the pixel electrodes 79 and perform chemical mechanical polishing (CMP) so as to flatten the surface of the pixel electrodes 79. However, the use of CMP is very likely to form disk-shaped hollows near the center and the edge portions, which results in insufficient flatness for optics and thus reducing the light-emitting efficiency of the liquid crystal display.
Moreover, the temperature characteristics of various materials such as silicon substrate, insulating silicon oxide layers and metal layers can be well-controlled due to mature semiconductor manufacturing processing so that the fabricated device functions correctly in the electrical performance over a wide operation temperature range. Whereas, due to the difference between the coefficients of thermal expansion of the various materials and thus the variation of tension, the chips diced form the wafer may become deformed. This will seriously affect the optical flatness on the surface of the display and will, more seriously, damage or crack the display because of non-uniformity of the liquid crystal layer.
Therefore, in view of the aforementioned drawbacks of the conventional structure of LCOS or SIRLCD, there is need in providing an improved SIRLCD and a method for manufacturing the SIRLCD, in which a simple structure is provided so as to simplify the manufacturing processing and reduce the cost.
Accordingly, it is the primary object of the present invention to provide a reflective-type liquid crystal display, in which an interface module between an optical module and a control module is formed so that the optical module and the control module are independently fabricated and then combined by the interface module, thereby improving the product yield and reliability.
It is another object of the present invention to provide a reflective-type liquid crystal display, in which an interface module between various control modules is formed so that the control modules are combined to provide multiple functions.
It is still another object of the present invention to provide a method for manufacturing a reflective-type liquid crystal display, in which a plurality of conductive plugs are disposed on a substrate so as to form an interface module by etching the substrate to comprise tips after an optical module is formed on the substrate, so that the interface module is combined with a control module.
It is still another object of the present invention to provide a method for manufacturing a reflective-type liquid crystal display, in which a control module is manufactured by using semiconductor manufacturing processing to comprise contacts on the surface so as to combine with an interface module.
It is still another object of the present invention to provide a method for manufacturing a reflective-type liquid crystal display, in which a control module is formed on a substrate comprising conductive plugs so as to combine with other control modules through an interface module disposed on the substrate.
In order to achieve the foregoing objects, the present invention provides a reflective-type liquid crystal display, comprising: an optical module, comprising at least one liquid crystal layer and a plurality of pixel electrodes for displaying images; a control module, comprising a plurality of control circuits; and an interface module for connecting said optical module and said control module so that said optical module and said control module are manufactured independently so as to improve product yield and reduce fabrication cost.
Other and further features, advantages and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings are incorporated in and constitute a part of this application and, together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.